1. Field of the Invention
The present invention relates to total hip arthroplasty, and, more particularly, to a method and apparatus for performing a minimally invasive total hip arthroplasty.
2. Description of the Related Art
Orthopaedic procedures for the replacement of all, or a portion of, a patient""s joint have been developed over the last 30 years. Currently, the procedures used to prepare the bone and seat the implants are-generally referred to as open procedures. For the purpose of this discussion, the term open procedure will refer to a procedure wherein an incision is made through the skin and underlying tissue to fully expose a large portion of the particular joint surface. In the case of a total hip arthroplasty, the typical incision required is approximately 25 centimeters (10 inches) long. After the initial incision in the skin, the internal wound may be enlarged in order to fully expose the areas to be prepared. While this approach provides surgeons with an excellent view of the bone surface, the underlying damage to the soft tissue, including the muscles, can lengthen a patient""s rehabilitation time after surgery. While the implants may be well fixed at the time of surgery, it may be several weeks or perhaps months before the soft tissues violated during surgery can be fully healed.
The present invention provides an improved method and apparatus for performing a minimally invasive total hip arthroplasty. A total hip arthroplasty can be performed in accordance with the teachings of the current invention utilizing two incisions with the size of each of the wounds developed on the surface being substantially constant throughout the depth of the wound. The first incision is an anterior incision approximately 3.75-5 centimeters (1.5-2 inches) in length made in line with the femoral neck and the central axis of the acetabulum. The second incision is a posterior incision approximately 2.5-3.75 centimeters (1-1.5 inches) positioned to be generally in axial alignment with the femoral shaft.
The femoral head is severed from the femoral shaft and removed through the anterior incision. The acetabular cup is placed in the acetabulum through the anterior incision, while the posterior incision is used to prepare the femoral shaft to receive a femoral stem. A femoral stem is inserted through the posterior incision and positioned in the femoral shaft. Procedures performed through the posterior incision may be observed through the anterior incision and vice versa.
For the purpose of the following discussion, a total hip arthroplasty is defined as a replacement of the femoral head with or without the use of a separate acetabular component. The specific designs which can be utilized in accordance with the present invention include a total hip replacement and a bipolar or monopolar endo prosthesis. The technique is suitable for cemented or cementless anchorage of the components.
The invention, in one form thereof, comprises a method of performing a total hip arthroplasty. The method of this form of the current invention includes the steps of: making an anterior incision, making a posterior incision, preparing an acetabulum to receive an acetabular cup through the anterior incision, seating an acetabular cup in said acetabulum through the anterior incision, preparing a femur to receive a femoral stem, and seating the femoral stem in the femur.
The invention, in another form thereof, comprises a method of performing a total hip arthroplasty. The method of this form of the current invention includes the steps of: preparing a femur to receive a femoral stem, placing a protective bag over the femoral stem, and seating the femoral stem in the femur.
The invention, in another form thereof, comprises a method of performing a total hip arthroplasty. The method of this form of the current invention includes the steps of: placing the patient in supine position; palpating the femoral neck and making an anterior incision of about 3.75-5 centimeters (1.5-2 inches) in line with the femoral neck and the central axis of the acetabulum; performing a blunt dissection of the muscle exposed by the anterior incision to expose the capsule of the hip joint; incising the capsule of the hip joint; retracting a portion of the capsule to visually expose the femoral neck; utilizing an osteotomy guide to mark a cut path along which a cut will be made to remove the femoral head and a portion of the femoral neck; cutting along the cut path; incising the ligamentum teres femoris; in situ morselizing the cut away femoral head an neck as necessary for removal through the anterior incision; removing the morsel of the femoral neck and head through the anterior incision; reaming the acetabulum; seating the appropriate acetabular cup in the reamed acetabulum; inserting a curved awl having a substantially straight distal end into the anterior incision; aligning the distal end of the awl with the femoral axis; palpating the distal end of the awl and making a posterior incision having a length of about 2.5-3.75 centimeters (1-1.5 inches at the location of the distal end of the awl; performing a blunt dissection to provide an access through the posterior incision to the femoral shaft; threading a retractor into he recess formed between the posterior incision and the femoral shaft; passing a guide wire through the retractor and into the cancellous bone of the femoral shaft; positioning the guide wire in the cannula of a femoral reamer; reaming the femoral shaft with the femoral reamer using the guide wire to locate the cancellous bone of the femur; observing the reaming activity through the anterior incision; removing the moral reamer; utilizing the guide wire to guide a rasp to the femoral shaft; positioning he rasp in the femoral shaft while observing through the anterior incision; removing the guide wire; removing the retractor from the posterior incision; positioning a trial acetabular liner in the acetabular cup through the anterior incision; affixing a provisional neck to the rasp through the anterior incision; affixing a provisional head to the provisional neck through the anterior incision; performing a trial reduction with the trial acetabular liner, provisional neck and provisional head in place; dislocating the provisional head; removing the trial acetabular liner through the anterior incision; removing the provisional neck and head through the anterior incision; removing the rasp through the posterior incision; seating a final acetabular liner in the acetabular cup through the anterior incision; inserting a femoral implant through the posterior incision; inserting a final femoral head through the anterior incision; affixing the fi al femoral head to the femoral implant; reducing the hip; and closing the incisions.
In one form of the current invention, the step of positioning a rasp in the femoral shaft comprises: locking the rasp to a rasp handle having a cannular insertion member with a distal rasp engagement guide and an elongate aperture sized to accommodate a flexible cable, engagement slot for selectively engaging an end of the flexible cable, a selectively actuatable grip operable to tension the flexible cable, a lock for selectively locking the grip in a position to tension the flexible cable, and an impact surface for receiving blows to place or remove the rasp; positioning the guide wire in a cannula of the rasp and he cannula of the rasp handle; guiding the rasp and the cannular insertion member through the posterior retractor to a proximal end of the femoral shaft using the guide wire; striking the impact surface to position the rasp within the femoral shaft; unlocking the grip; releasing the flexible cable from the engagement slot; and removing e rasp handle.
In one form of the current invention, the step of locking the rasp to a rasp handle comprises: engaging a distal end of the flexible cable in the rasp; inserting the flexible cable through the elongate aperture of the rasp handle; guiding the distal rasp engagement guide into a rasp engagement guide receiving portion on the rasp; engaging the proximal end of the flexible cable in the engagement slot; and tensioning the flexible cable.
In one form of the current invention, the step of removing the rasp from the femoral shaft comprises: reinserting the flexible cable through the elongate aperture of the cannular insertion member (the flexible cable remains engaged with the rasp placed in the femur and protrudes from the posterior wound); reinserting the cannular insertion member through the posterior retractor; guiding the distal rasp engagement guide into the rasp engagement receiving portion on the rasp; engaging the proximal end of the flexible cable in the engagement slot; tensioning the flexible cable; and impacting the impact surface to remove the rasp from the femoral shaft.
The invention, in another form thereof, comprises a method of removing a femoral neck and head. The method of this form of the current invention includes the steps of: making an anterior incision in line with the femoral neck; providing an osteotomy guide having a handle an with an alignment portion and a cut guide affixed to the handle; aligning the alignment portion with the femoral axis, marking a cut path defined by the cut guide, and cutting along the cut path to remove a cut portion comprising a portion of the femoral neck and the femoral head.
The invention, in another form thereof, comprises a method of making a posterior incision aligned with a longitudinal axis of the femur. The method of this form of the current invention includes the steps of making an anterior incision aligned with the femoral neck, providing an awl having a handle and a curved awl shaft having a distal end, aligning the distal e d with the longitudinal axis of the femur, palpating a location of the distal end of the awl, and making a posterior incision at the location of the distal end of the awl.
The invention, in another form thereof, comprises a method of preparing a femur to receive a femoral implant. The method of this form of the current invention includes the steps of: removing the femoral head and neck as necessary, making a posterior incision of approximately 2.5-3.75 cm which is substantially aligned with the central axis of the femoral shaft, performing a blunt dissection to provide an access through the posterior incision to pose the femoral shaft, inserting a retractor comprising a tunnel sized for insertion through the access into the access, and preparing the femur to receive a femoral implant through the retractor.
The invention, in another form thereof, comprises an osteotomy guide having a handle allowing use of the osteotomy guide a distance from a femur as well as an alignment portion and a cut guide affixed to the handle.
The invention, in another form thereof, comprises an awl having a handle and an awl shaft with a distal end. The distal end of the awl shaft is adapted to be inserted into an anterior incision and align with the longitudinal axis of a femur to locate a posterior incision operable to expose a proximal end of the femur.
The invention, in another form thereof, comprises a retractor formed of a tunnel sized for insertion through an access leading to the femoral shaft in a body.
The invention, in another form thereof, comprises a rasp handle having an insertion member with engagement means for selectively engaging a cable which is affixable to a rasp. In one form of the current invention, the engagement means comprises an engagement slot for selectively engaging the cable.
The invention, in another form thereof, comprises a provisional femoral neck apparatus including a provisional femoral neck having a hollow, substantially cylidrical body. A spring biased lo king piston is provided and housed within said hollow cylindrical body. The locking piston includes a tapered body portion. Application of a radial force to the tapered body portion moves the locking piston against the biasing force of the spring. The blades of a forceps may be utilized to apply the radial force to the tapered portion of the locking piston.
The invention, in another form thereof, comprises a provisional prosthetic femoral neck having a guide surface and a provisional femoral stem including a mate to the guide surface. The guide surface is piloted to the mate to join the femoral neck and the femoral stem. In one form of the current invention, the femoral neck is substantially cylindrical and i piloted to the femoral stem in a radial direction.
The apparatus and method of the current invention advantageously allow a total hip arthroplasty to be perform d in a minimally invasive way, which hastens patient recovery.